Special Formats Displays
Blaze Display Technology Co., Ltd. | Updated: Nov 27, 2018
The display world started with 4:3 aspect ratios, and then "SXGA" used 5: 4. The migration to widescreen 16: 9 has now been largely completed and mobile devices are extending the image format to 2: 1. However, there are applications that cannot do much with the display areas available in mainstream formats. For example, in a signpost, a very slim display would suffice. There are various approaches to producing such a display.
Unusual display formats
In order to meet the demand for LCDs with special aspect ratios, there are basically two approaches. Either:
l a display is developed and manufactured precisely, or
l a large-format display is cut to size.
Both methods have advantages and disadvantages: The development of a customer-specific TFT requires a lot of development cost up to several €100,000s, and the number of pieces must be high enough that it is worth stopping the production line to convert to the special format.
It is sometimes easier to cut a suitable display from a commercial panel. In addition to the display panel itself, the LED backlight, the frame (bezel) and the entire film stack must be adapted. Taking a longitudinal section usually creates displays with aspect ratios of e.g. 32: 9 or 16: 3. What are the requirements for a display to be suitable for cutting?
Original displays in unusual formats
There are also displays needed for some applications with square or round formats. Small displays of this type may use a single-chip TFT controller that is integrated as chip-on-glass on the panel. The chip combines the functions of the timing controller, drivers for rows and columns and also the frame buffer. The host interface does not work in a PC environment, but with an ARM or other microcontroller. In addition to a MIPI bus, the display can be updated via SPI or a CPU bus. To relieve the burden on the system controller, the color depth can be reduced from 24 to 16 bits in many applications.
Single-chip displays are common in diagonals up to 5" and with a resolution up to 720x720. There is a 26.5" display from LG Display, on the other hand, that offers a high resolution in square format with a 1920 x 1920 pixel format and is connected via LVDS. Displays with an aspect ratio of 3: 2 are used in tablet computers such as Apple iPad.
Displays with a circular image section
Smartwatches or fitness trainers often use round displays. The control lines for rows and columns are routed at the edge of the viewing area. In the display shown in Figure 6, the driver is a single-chip solution at the lower end of the glass, so that the housing must be shaped accordingly.
Conclusion
Displays with special formats are used in confined spaces, or where the content needs a certain format. Larger displays can be made by cutting, while smaller ones tend to be already made with special dimensions and shapes. In combination with a touchscreen, a display can enable new user interfaces and interactivity can make the end product more versatile for the user and more attractive for the end user. The designer can have a large variety of displays with special formats to choose from.